Conventional water pump bearings for water pump assembly used in cooling systems for automobiles and agricultural and industrial purposes are disposed with a plurality of rolling elements 6 between an inner race 2 and an outer race 4, as illustrated in FIG. 1. A retainer 8 is formed for maintaining the plurality of rolling elements in a prescribed space (S). A seal 10 is coupled to a tip end of an opening of the space (S) formed between the inner race 2 and the outer race 4 for preventing foreign particles from entering the space. The seal 10 is made of a reinforced frame 12 of cold rolling material bent in a prescribed shape, abutted by a sealing material 14 and push-fitted into a hitching groove band 4a formed at an outer race 4 of a bearing.
The sealing material 14 is formed therein, that is, at an area abutted by an outer surface of the inner race 2, with a first seal lip 14a and a second seal lip 14b. The first seal lip 14a is formed within the space (S) to prevent grease in the space (S) from leaking and the second seal lip 14b is formed outside of the space (S) to prevent foreign particles or moisture mixed therewith from entering the space (S) from the outside.
Recently, due to improved performance of engines used in water pumps, demand for sophisticated bearings has gradually increased, resulting in the need to improve the sealing and foreign particle preventing function of the seal that greatly affects the performance of bearings.
There are many factors that cause damage to water pump bearings. A malfunctioning of lubrication caused by grease leakage and penetration of foreign particles, moisture and mixture therewith into the bearings are the most common causes. Life of bearings is directly related to grease leakage and penetration of moisture, foreign particles and mixture therewith into the bearings.
Although the first seal lip 14a and the second seal lip 14b in conventional bearings for water pumps have somewhat helped repel grease leakage and penetration of moisture and foreign particles, there are still drawbacks in that the bearings are always exposed to outside foreign particles failing to fully prevent mixture or penetration thereof. And particularly, when bearings are exposed to water, lots of moisture can seep in to cause damage to the bearings.